Macrobenthos relative to the oxygen minimum zone on the East Indian margin, Bay of Bengal

TitleMacrobenthos relative to the oxygen minimum zone on the East Indian margin, Bay of Bengal
Publication TypeJournal Article
Year of Publication2015
AuthorsRaman A.V, Damodaran R., Levin L.A, Ganesh T., Rao Y.KV, Nanduri S., Madhusoodhanan R.
JournalMarine Ecology-an Evolutionary Perspective
Date Published2015/09
Type of ArticleArticle
ISBN Number0173-9565
Accession NumberWOS:000358729600034
KeywordsBay of Bengal diversity; benthic processes; Central chile; community structure; continental-margin; deep-sea; diversity; East Indian margin; faunal assemblages; hypoxia; macrobenthos; organic-matter; Oxygen minimum zone; peru margin; western bay

The Bay of Bengal remains one of the least studied of the world's oxygen minimum zones (OMZs). Here we offer a detailed investigation of the macrobenthos relative to oxygen minimum zone [OMZ - DO (dissolved oxygen), concentration <0.5ml1(-1)] at 110 stations off the North East Indian margin (16(0) and 20(0)N) featuring coastal, shelf and slope settings (10-1004m). Macrobenthos (>0.5mm) composition, abundance and diversity were studied in relation to variations in depth, dissolved oxygen, sediment texture and organic carbon. Using multivariate procedures powered by SIMPROF analysis we identified distinct OMZ core sites (depth 150-280m; DO 0.37ml1(-1)) that exhibited dense populations of surface-feeding polychaetes (mean 2188 ind. m(-2)) represented by spionids and cossurids (96%). Molluscs and crustaceans were poorly represented except for ampeliscid amphipods. The lower OMZ sites (DO>0.55mll(-1)) supported a different assemblage of polychaetes (cirratulids, amphinomids, eunicids, orbinids, paraonids), crustaceans and molluscs, albeit with low population densities (mean 343 ind. m(-2)). Species richness [E(S-100)], diversity (Margalef d; H') and evenness (J') were lower and dominance was higher within the OMZ core region. Multiple regression analysis showed that a combination of sand, clay, organic carbon, and dissolved oxygen explained 62-78% of the observed variance in macrobenthos species richness and diversity: E(S-100) and H'. For polychaetes, clay and oxygen proved important. At low oxygen sites (DO <1mll(-1)), depth accounted for most variance. Residual analysis (after removing depth effects) revealed that dissolved oxygen and sediment organic matter influenced 50-62% of residual variation in E(S-100), H' and d for total macrofauna. Of this, oxygen alone influenced up to similar to 50-62%. When only polychaetes were evaluated, oxygen and organic matter explained up to 58-63%. For low oxygen sites, organic matter alone had the explanatory power when dominance among polychaetes was considered. Overall, macrobenthic patterns in the Bay of Bengal were consistent with those reported for other upwelling margins. However, the compression of faunal gradients at shallower depths was most similar to the Chile/Peru margin, and different from the Arabian Sea, where the depth range of the OMZ is two times greater. The Bay of Bengal patterns may take on added significance as OMZs shoal globally.

Short TitleMar. Ecol.-Evol. Persp.
Student Publication: